Certain electronics must be soldered at high temperatures and require high heat deflection temperature (HDT) materials. Such materials typically have high melting points and thus must be melt processed at relatively high temperatures. PCT is a high-melting polyester with a melting point of about 290.degree. C. and, consequently, is very challenging to formulate while retaining good molecular weight. In addition to good melt stability, good dimensional stability, flammability, and toughness characteristics are important.
In the industry, use of tougheners in polymers has been known for some time. However, in most cases, HDT is sacrificed in order to achieve the characteristic of toughness.
U.S. Pat. No. 5,021,495 by Minnick discloses high temperature glass fiber reinforced, flame retardant PCT formulations. In the Minnick patent, it is shown that use of functional olefins (not acrylate/methacrylate rubber impact modifiers) can improve flame retardancy without hurting dimensional stability. These materials did not improve the toughness of the PCT formulations.
U.S. Pat. No. 5,428,086 discloses high temperature glass fiber reinforced, flame retardant PCT formulations. This patent discloses that certain additives can compromise the dimensional stability of the PCT formulation.